Far cleaner than conventional incinerators, this new type of plant converts local trash into heat and electricity. Dozens of filters catch pollutants, from mercury to dioxin, that would have emerged from its smokestack only a decade ago.

Denmark now has 29 such plants, serving 98 municipalities in a country of 5.5 million people, and 10 more are planned or under construction. Across Europe, there are about 400 plants, with Denmark, Germany and the Netherlands leading the pack in expanding them and building new ones.

By contrast, no new waste-to-energy plants are being planned or built in the United States, the Environmental Protection Agency says — even though the federal government and 24 states now classify waste that is burned this way for energy as a renewable fuel, in many cases eligible for subsidies. There are only 87 trash-burning power plants in the United States, a country of more than 300 million people, and almost all were built at least 15 years ago.